Imaging apparatus utilizing an imaging device such as a CCD or a CMOS have recently spread, such apparatus shooting an optical image of an object formed on a light-receiving surface of the imaging device by a group of imaging lenses. The image obtained by such an imaging apparatus has a resolution corresponding to the number of light-receiving pixels on the light-receiving surface and the resolution of the imaging lens.
Therefore, increase in the number of the light-receiving pixels and improvement in the resolution of the imaging lens are effective for improving the resolution of the image obtained by the imaging apparatus. For example, the resolution of an image obtained by such an imaging apparatus can be improved by increasing the density of light-receiving pixels provided on the light-receiving surface and improving the resolution of the imaging lens group such that a point image projected on the light-receiving surface through the imaging lens group stays within the range of one light-receiving pixel.
As a result of technological advances made in recent years, it has become relatively easy to increase the density of light-receiving pixels forming an imaging device. One effective way of improving the resolution of a group of imaging lenses is to reduce errors in shaping and assembling lenses forming the imaging lens group. However, it is highly difficult to improve accuracy of manufacture of such lenses, i.e., accuracy of processing, assembling, and adjustment.
As another approach toward improved resolution, JP-A-2009-141742 (Patent Document 1) discloses a method of improving the resolution of an image obtained by an imaging apparatus, the method including the step of performing signal processing of the image based on a PSF (point spread function).
JP-A-2007-72558 (Patent Document 2) discloses an image processing method including the steps of dividing frequency components of an input image into several bands using a band division filter and convolving only low-frequency components of the input signal with the inverse of point spread functions to duplicate convolved computational loads.